Histological evaluation disqualifies IMT and calcification scores as surrogates for grading coronary and aortic atherosclerosis

Background/objectives Carotid intimal media thickness (IMT) and coronary calcium scores (CCS) are thought to reflect atherosclerotic burden. The validity of this assumption for IMT is challenged by recent meta-analyses; for CCS by absence of a relationship between negative scores, and freedom of future events. As such, we considered evaluation of the relationship between tissue IMT and CCS, and extend of atherosclerotic disease relevant.
Methods Analyses were performed on donor aortas obtained during renal graft procurement, and on coronary arteries collected during heart valve procurement for tissue donation. Movat pentachrome and Hematoxylin staining was performed, and the degree of atherosclerosis histologically graded. IMT and presence of calcium deposits were quantified on graded tissue sections.
Results 304 aortas and 185 coronary arteries covering the full atherosclerotic spectrum were evaluated. Aortas and coronaries showed similar relationships between tissue IMT and degree of atherosclerosis, with gradual increase in tissue IMT during earlier phases of atherosclerosis (r = 0.68 and r = 0.30, P < 0.00001 for aorta and coronaries respectively), followed by plateauing of the curve in intermediate and advanced stages. Results for tissue IMT reveal high variability, resulting in wide confidence intervals. Results for CCS are similar for aorta and coronaries, with calcium depositions limited to advanced lesions.
Conclusions Histological IMT measurements for the aorta and coronaries show large variations around the trend and plateauing of, and possibly reductions in IMT in late stage atherosclerotic disease. These observations for the aorta and coronaries may (partly) explain the limited benefit of including carotid IMT in risk prediction algorithms.